Ozone has a strong oxidizing power. After oxidizing other substances, ozone decomposes into harmless substances such as oxygen. Therefore, ozone is widely used for, e.g., cleaning process, sterilization process, and deodorization process in the fields of semiconductor device manufacturing, food production, water treatment, etc.
Many of ozone generators in actual use are of the silent discharge type.
Each ozone generator of the silent discharge type includes two electrodes facing each other via a dielectric, and a gap (a discharge gap) is provided between the two electrodes. When a high voltage is applied between the two electrodes, a silent discharge occurs in the discharge gap. Ozone is generated by causing a source gas containing oxygen to flow into the discharge gap, where the source gas is ozonized.
The ozone generators of the silent discharge type are classified into the plate type and the tube type according to their structural difference. The plate-type ozone generator includes an ozone generation unit in a plate shape. On the other hand, the tube-type ozone generator includes an ozone generation unit in a tube shape.
While the plate-type ozone generator is generally unsuitable for upsizing, the tube-type ozone generator does not have such a disadvantage and is capable of operating with an increased number of the units. Thus, the tube-type ozone generator is advantageous in that it can be upsized easier than the plate-type one.
For example, Patent Documents 1 and 2 describe prior art related to the present invention.
Patent Document 1 discloses a tube-type ozone generator. This ozone generator includes a glass dielectric tube having a cylindrical shape and a spherically closed end. A first electrode made of a metal such as stainless steel is formed on the inner surface of the dielectric tube, specifically, on a portion of the inner surface extending from the spherical end to the side of the dielectric tube.
A rod-shaped high-voltage feeder electrically connected to a high-voltage power supply is provided inside the dielectric tube. The first electrode is electrically connected to the high-voltage feeder through a stainless steel wool material. A cylindrical second electrode surrounds the outer surface of the dielectric tube. A discharge gap is provided between the dielectric tube and the second electrode.
A source gas is ozonized while passing through the discharge gap under application of a high voltage. The ozonized gas is let out through an ozonized gas outlet near which the spherical end is located.
Patent Document 2 also discloses a tube-type ozone generator similar to that of Patent Document 1. Specifically, the ozone generator of Patent Document 2 includes a dielectric electrode corresponding to the glass dielectric tube, and a conductive film corresponding to the first electrode. The conductive film is formed on the inner surface of the dielectric electrode by vapor deposition or thermal spraying, for example.
A feeder axis corresponding to the high-voltage feeder has stainless steel constituent wires attached thereto and bundled in a twisted brush-like shape. These constituent wires are pressed onto a cylinder made of a metal plate and attached to part of the inner surface of the conductive film, thereby electrically connecting the conductive film to the feeder axis.